imports, go/ast/astutil: do not make grouped imports non-grouped when removing

import (
		"fmt"
		"strings"
	)

When deleting "fmt" import statement, code should be converted to the
following code.

	import (
		"strings"
	)

Instead of

	import "strings"

Diff becomes nicer by this change and it avoids that rewriting grouped
imports non-grouped may result in confusion comments.

Example:

	// comment 1
	import (
		"fmt"
	        // comment 2
		"strings"
	)

should be

	// comment 1
	import (
	        // comment 2
		"strings"
	)

instead of

	// comment 1
        // comment 2
	import "strings"

Fixes golang/go#18051

Change-Id: I3c07b70b657191eacf83c3197a965e587286c950
Reviewed-on: https://go-review.googlesource.com/36853
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Robert Griesemer <gri@golang.org>

go/ast/astutil/imports.go

@@ -234,16 +234,17 @@ func DeleteNamedImport(fset *token.FileSet, f *ast.File, name, path string) (del
 					}
 				}
 
-				gen.Lparen = token.NoPos // drop parens
 				spec := gen.Specs[0].(*ast.ImportSpec)
-				if spec.Doc != nil {
-					// Move the documentation above the import statement.
-					gen.TokPos = spec.Doc.End() + 1
-				}
 
+				// Move the documentation right after the import decl.
+				if spec.Doc != nil {
+					for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Doc.Pos()).Line {
+						fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
+					}
+				}
 				for _, cg := range f.Comments {
 					if cg.End() < spec.Pos() && fset.Position(cg.End()).Line == fset.Position(spec.Pos()).Line {
-						for fset.Position(gen.TokPos).Line != fset.Position(spec.Pos()).Line {
+						for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Pos()).Line {
 							fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
 						}
 						break

go/ast/astutil/imports_test.go

@@ -944,7 +944,9 @@ import (
 `,
 		out: `package main
 
-import "fmt"
+import (
+	"fmt"
+)
 `,
 	},
 	{
@@ -961,7 +963,7 @@ import y "fmt"
 import y "fmt"
 `,
 	},
-	// Issue #15432
+	// Issue #15432, #18051
 	{
 		name: "import.19",
 		pkg:  "fmt",
@@ -975,8 +977,10 @@ import (
 )`,
 		out: `package main
 
-// Some comment.
+import (
-import "io"
+	// Some comment.
+	"io"
+)
 `,
 	},
 	{
@@ -993,9 +997,11 @@ import (
 )`,
 		out: `package main
 
-// Some
+import (
-// comment.
+	// Some
-import "io"
+	// comment.
+	"io"
+)
 `,
 	},
 	{
@@ -1014,11 +1020,13 @@ import (
 )`,
 		out: `package main
 
-/*
+import (
-	Some
+	/*
-	comment.
+		Some
-*/
+		comment.
-import "io"
+	*/
+	"io"
+)
 `,
 	},
 	{
@@ -1034,9 +1042,11 @@ import (
 )`,
 		out: `package main
 
-/* Some */
+import (
-// comment.
+	/* Some */
-import "io"
+	// comment.
+	"io"
+)
 `,
 	},
 	{
@@ -1052,8 +1062,10 @@ import (
 )`,
 		out: `package main
 
-// comment 2
+import (
-import "io"
+	// comment 2
+	"io"
+)
 `,
 	},
 	{
@@ -1067,7 +1079,9 @@ import (
 )`,
 		out: `package main
 
-import "io" // comment 2
+import (
+	"io" // comment 2
+)
 `,
 	},
 	{
@@ -1081,7 +1095,9 @@ import (
 )`,
 		out: `package main
 
-import /* comment */ "io"
+import (
+	/* comment */ "io"
+)
 `,
 	},
 	{
@@ -1095,7 +1111,9 @@ import (
 )`,
 		out: `package main
 
-import "io" /* comment */
+import (
+	"io" /* comment */
+)
 `,
 	},
 	{
@@ -1109,7 +1127,9 @@ import (
 )`,
 		out: `package main
 
-import "io"
+import (
+	"io"
+)
 `,
 	},
 	{
@@ -1123,7 +1143,9 @@ import (
 )`,
 		out: `package main
 
-import "io"
+import (
+	"io"
+)
 `,
 	},
 	{
@@ -1139,7 +1161,9 @@ import (
 		out: `package main
 
 // comment 1
-import "io" // comment 2
+import (
+	"io" // comment 2
+)
 `,
 	},
 	{
@@ -1155,7 +1179,9 @@ import (
 		out: `package main
 
 // comment 1
-import "io"
+import (
+	"io"
+)
 `,
 	},
 	{
@@ -1171,7 +1197,9 @@ import (
 		out: `package main
 
 // comment 1
-import /* comment 2 */ "io"
+import (
+	/* comment 2 */ "io"
+)
 `,
 	},
 	{
@@ -1188,7 +1216,9 @@ import (
 		out: `package main
 
 // comment 1
-import /* comment 2 */ i "io"
+import (
+	/* comment 2 */ i "io"
+)
 `,
 	},
 	{
@@ -1205,7 +1235,9 @@ import (
 		out: `package main
 
 // comment 1
-import i "io"
+import (
+	i "io"
+)
 `,
 	},
 	{
@@ -1222,7 +1254,49 @@ import (
 		out: `package main
 
 // comment 1
-import i "io"
+import (
+	i "io"
+)
+`,
+	},
+	{
+		name: "import.35",
+		pkg:  "fmt",
+		in: `package main
+
+// comment 1
+import (
+	"fmt"
+	// comment 2
+	"io"
+)`,
+		out: `package main
+
+// comment 1
+import (
+	// comment 2
+	"io"
+)
+`,
+	},
+	{
+		name: "import.36",
+		pkg:  "fmt",
+		in: `package main
+
+/* comment 1 */
+import (
+	"fmt"
+	/* comment 2 */
+	"io"
+)`,
+		out: `package main
+
+/* comment 1 */
+import (
+	/* comment 2 */
+	"io"
+)
 `,
 	},
 }

imports/fix_test.go

@@ -188,7 +188,9 @@ _, _ := bytes.Buffer, bytes.NewReader
 `,
 		out: `package foo
 
-import "bytes"
+import (
+	"bytes"
+)
 
 func bar() {
 	_, _ := bytes.Buffer, bytes.NewReader
@@ -747,7 +749,9 @@ func main() { fmt.Println() }
 `,
 		out: `package main
 
-import "fmt"
+import (
+	"fmt"
+)
 
 func main() { fmt.Println() }
 `,
@@ -775,6 +779,27 @@ import (
 )
 
 func main() {}
+`,
+	},
+
+	{
+		name: "do not make grouped imports non-grouped",
+		in: `package p
+
+import (
+	"bytes"
+	"fmt"
+)
+
+var _ = fmt.Sprintf
+`,
+		out: `package p
+
+import (
+	"fmt"
+)
+
+var _ = fmt.Sprintf
 `,
 	},
 }